It is the purpose of the proposed research to determine the electrical parameters required to prevent and treat the loss of bone mass, or decrease in density, that occurs in disuse osteoporosis. Several animal models, both in vitro and in vivo, will be used in which loss of bone mass or decrease in bone density is induced by various means. Bone density, cortical thickness, cross-sectional area, porosity, and breaking strength will be determined for experimental and control bones in 18-day-old fetal rat tibiae grown in vitro in 60% 02, in tibiae of sciatic denervated mature rabbits, and in tibiae of cast immobilized mature rabbits. The experimental bones will be subjected to various time varying electrical fields (capacitive coupling). The effect of the electric fields on preventing or treating osteoporosis by increasing bone formation and decreasing bone resorption will be determined in vitro in 18-day-old fetal rats and in vivo in sciatic denervated rat tibiae by determining 14C-proline and 3H-glucosamine uptake and release. It is anticipated that the proposed research will determine the proper electrical parameters required to prevent decrease in bone density in bone density in these animal models. The stage will then be set to translate these findings into clinical trials on the use of capacitive coupling in preventing/treating osteoporosis in the human.